This invention relates in general to ensuring fluid lock in an indwelling catheter, for use in the cardiovascular system, such as a hemo-dialysis catheter.
The hemo-dialysis catheter is maintained in the patient between dialysis procedures. In order to avoid blood clot within the catheter, a charge of heparinized saline is placed in the catheter to displace the blood and prevent blood clot. This state is called heparin lock or, more generically, fluid lock. The time between blood cleaning procedures (often called dialysis interval time) generally is two to four days.
In order to avoid infection, an antibiotic solution might be used in the catheter to displace the blood and create a fluid lock. Antibiotic heparin might be employed for the fluid lock to prevent both blood clot and infection during the dialysis interval time.
In a typical catheter having a central aspiration lumen and an annular infusion lumen, the openings near the distal end of the infusion lumen are staggered axially. Accordingly, when the heparinized saline is injected into the annular infusion lumen, one of two things occur that negates the function of the heparinized saline and tends to allow a blood clot to form.
In one situation, the heparinized saline exits from the proximal most port thereby failing to displace the blood distal of that exit port.
In another situation, the heparinized saline may be inserted with sufficient flow speed to displace all of the blood in the annular catheter. However, the patient's blood gradually circulates through the openings in the annular lumen, displacing the heparinized saline allowing a blood clot to develop over the zone between proximal and distal openings in the annular catheter.
The heparinized saline is locked into the lumens and this state is often referred to as heparin lock. A blood clot at the distal zone prevents the heparin lock from performing its anti-clotting function at that zone.
Accordingly, it is an object of this invention to provide a long term indwelling catheter design that maximizes the effect of the heparin lock as well as maximizing the effect of any other fluid lock such as when an antibiotic fluid is used.
It is also important in these catheter designs that the catheter have a smooth surface in order to provide ease of insertion.